PROJECT SUMMARY/ABSTRACT Alcohol and drug use (e.g., tobacco and marijuana use) are major public health problems affecting large proportions of youth. Alcohol and drug use also disproportionately burden certain youth populations, such as sexual minority youth (SMY; i.e., adolescents who identify as gay/lesbian or bisexual, or who have same- gender sexual behaviors or attractions). Compared with heterosexual youth, SMY have up to 600% higher odds of lifetime drug and alcohol use. Despite these substantial disparities, few evidence-based interventions exist for reducing alcohol and drug use among SMY. Nevertheless, SMY who report having supportive adults at school, greater school connectedness, and lower bullying victimization have lower drug and alcohol use. Therefore, an intervention that trains school staff (e.g., teachers, principals, nurses, counselors) to better understand SMY, support SMY, and engage in positive bystander behaviors that protect SMY from bullying victimization may reduce sexual-orientation disparities in drug and alcohol use. Furthermore, many school staff desire to support SMY, but they report a lack of training as their primary impediment. To address these gaps, I will execute two Specific Aims. In Aim #1, I will develop an online e-learning intervention aimed at improving school staff?s knowledge, skills, and self-efficacy for supporting SMY. Using the intervention mapping approach, I will develop, user-test, and refine intervention materials by: conducting focus groups with a School Staff Advisory Board; performing usability tests via think aloud interviews with school staff; and collaborating with professional e-learning developers. In Aim #2, I will pilot test the feasibility and preliminary efficacy of this school staff-based intervention using a two-armed cluster-randomized controlled trial. I will enroll high schools participating in the fully-funded survey infrastructure of the MetroWest Adolescent Health Survey (MWAHS), located outside Boston, Massachusetts, where sexual-orientation disparities in drug and alcohol use still exist. Biennially, the MWAHS administers surveys to all students in each school, providing ample student-level data. In tandem, I will collect new longitudinal survey data (baseline and 6-month follow-up) from all school staff within each enrolled school. This e-learning intervention is easily modifiable and economically scalable, making it apt for wide dissemination with the potential for population-level impact in reducing drug and alcohol use disparities. To successfully complete my research, I will acquire training in: (1) the development of stakeholder- informed interventions, particularly e-learning programs; (2) implementation science research; and (3) the design and analysis of experimental studies. Guided by a strong interdisciplinary mentorship team, my planned training activities include mentorship meetings, formal coursework, training institutes, scientific seminars, and research conferences. Upon successful completion of my research and training plans, I will be propelled towards achieving my long-term goal, which is to become an independent scientific researcher specializing in stakeholder-informed intervention science aimed at reducing drug and alcohol use disparities for SMY.